Preparation of ether acetals



RCOOCH=CH2 HOB.

Patented Sept. 7, 1948 UNITED STATES PATENT OFFICE PREPARATION OF ETHERACETALS Willard J. Croxall, Bryn Athyn, and Harry T. Neher, Bristol,Pa., assignors to Riihm & Haas Company, Philadelphia, Pa.,- acorporation of Delaware No Drawing. Application October 30, 1947, SerialNo. 783,210

6 Claims. (Cl. 260-.615)

I tion-in-part of our application, Serial No. 613,034,

filed August 27, 1945, now Patent 2,446,171, is particularly directed tothe preparation of acetals from ether alcohols and vinyl esters,particularly vinyl esters of saturated, aliphatic, monocarboxylic acidsof two to four carbon atoms.

The mechanism of this reaction may be accounted for at leasttheoretically as follows:

As a vinyl ester, there may be preferably used vinyl acetate, vinylpropicnate, vinyl butyrate, or other carboxylic ester, RCOOCH==CH2,wherein R is the organic residue of a carboxylic acid; but other estersmay be used, the carboxylic acid portion not being of importance, sinceit is eliminated in the reaction.

As an alcohol, R'OH, there may be used any organic compound containing anon-tertiary alcoholic hydroxyl and being free of interfering groups orgroups which react with or destroy the catalysts, such as amino groups.The alcohols may be aliphatic, cycloaliphatic, arylaliphatic, orheterocyclic aliphatic. compounds, the -OH group is attached to 9.---CH2 or --CH= group; that is, it is aliphatically bound andis notattached directly to the carbon atom of an aryl nucleus. The alcoholmay, therefore, be considered non-aromatic or aliphatic in character.Phenolic hydroxyl groups tend to give resinous products rather thanacetals.

Typical alcohols which may be used are methyl, ethyl, propyl, isopropyl,n-butyl, sec.-butyl, isobutyl, the various primary and secondary amyl,hexyl, octyl, decyl, dodecyl, myristyhcetyl, and octadecyl alcohols,allyl, methallyl, crotyl, undecenyl, and oleyl alcohols, benzyl alcohol,phenylethyl alcohol, tetrahydrofurfuryl alcohol, cyclohexanol, methylcyclohexanol, hexahydrobenzyl alcohol, terpineol,hydroxydlhydronordlcyclopentadiene, hydroabietyl alcohol,methoxyethanol, ethoxyethanol, isopropoxyethanol, butoxyethanol,octyloxyethanol, dodecyloxyethanol, octadecyloxyethanol,methoxyethoxyethanol, butoxyethoxyethanol, decyloxyethoxy-' In all such2 ethanol, cetyloxyethoxyethanol, methoxyethoxyethoxyethanol,butoxyethoxyethoxyethoxyethanol,2-ethylhexyloxyethoxyethoxyethoxyethoxyethanol,dodecyloxyethoxyethoxyethoxyethanol,-

allyloxyethanol, methallyloxyethanol, undecenyloxyethoxyethoxyethanol,oleyloxyethoxyethoxyethoxyethanol, ethoxypropanol, butoxypropanol,butoxyethoxypropanol, butoxypropoiwpropanol,2-ethylbutyloxypropoxyethoxyethanol, phenoxyethanol,tert.-butylphenoxyethanol, cresoxyethanol, tert.-octylphenoxyethanol,undecylphenoxyethanol, phenoxypropanol, phenoxypropoxypropanol,tert.-butylphenoxyethoxyethoxyethanol,isooctylphenoxyethoxyethoxyethoxyethoxyethanol,cyclohexyloxyethoxyethanol, methyl- BCOOH cH-cmcyclohexyloxyethoxyethoxyethoxyethanol, benzyloxyethoxycthoxyethanol,butylbenzyloxyethoxyethanol, hexahydrobenzyloxyethoxyethanol,alkoxypolyethoxyethanols having as many as twelve or more etherlinkages, and the like, polydihydrlc alcohols, including ethyleneglycol, propylene glycol, diethylene glycol, and the like, andsubstituted alcohols such as chlorohydrin, hydroxy esters such'as methylglycolate, ethyl lactate, or the like. Acetals prepared from hydroxyesters of unsaturated alcohols have been made the subject of anotherapplication, Serial No. 613,032, filed August 27, 1945. i

The mercury compound taken for a catalyst is preferably mercury oxide,but this mercury compound alone is not effective. in conjunction with astrongly acidic catalyst, such as a strong mineral 'acid, for examplesulfuric acid or tetraphosphoric acid or an ansolvc acid,'illustrated bythe highly efiective com plexes formed with boron trlfiuoride. The oxideand acid together form in situ a most efiective catalytic combination,which for practical purposes may be regarded as both a mercury catalystand a strongly acidic catalyst. It is not essential, however, that'thecombination be formed in situ, for preformed mercury salts, such asmercury sulfate or mercury phosphate, which themselves can yield astrong acid, as by hydrolysis, may be used. The reaction was found to bepromoted also by mercuric chloride, although the reaction then was notso rapid as with the combination formed in situ. Other effectivecatalysts are mercury acetate-sulfate and mercuryacetatetrichloroacetate.

It must be used Complexes formed from boron trifluoride and anoxygenated organic compound are particularly valuable acidic catalystsin conjunction with a mercury compound. Such complexes are readilysoluble in the reaction mixture, produce no troublesome by-products, andare readily disposed of at the end of the reaction. Coordinationcomplexes of boron trifluoride and an oxygenated organic compound aretypified by BFa.O(C2I-I5)2 or BFa.O(C4Ho)a from ethers, BFa.2CHaCOO1-1from carboxylic acids, BF:.C4H9OH or BFa.2C2H5OH from alcohols,BF:.CH:COCH: from'ketones, or BFaMx in general for such coordinationcomplexes.

The strongly acidic catalysts by themselves have not been found to leadto formation of acetals. Strong mineral acids alone, instead, tend tocause transesterification. Yet, when both mercury in the form of acompound and a strongly acidic catalyst are present, even though in thesame compound, acetal formation results. The combination of catalystspromotes the rather surprising reaction of an alcohol with an ester withdisplacement of a carboxylic acid.

There are required only catalytic amounts of mercury compound and ofstrongly acidic catalyst for the promotion of the acetal reaction. Assmall amounts as gram of mercury compound and /2 gram of strongly acidiccatalyst per gram mole of vinyl ester give relatively rapid. conversionsand fair yields of acetals. Smaller amounts of catalysts are effective,however, even though the yields may fall off slightly; Onegram portionsof both mercury compound and strongly acidic catalyst per gram mole ofvinyl ester, on the other hand, appear about optimum in respect to bothrate of reaction and yield with economy of time, materials, and effort.Higher proportions may be used, even 10 grams of both per gram mole ofester being satisfactory.

The optimum ratio of vinyl ester to alcohol is about the theoretical one(one to two), but, even with ratios of one to one, the final product canbe carried primarily to the acetal, particularly if vinyl ester is addedto alcohol. With such low ratios, some hemiacetal esters are usuallyformed, particularly when alcohol is added to vinyl ester, but thesehemiacetal esters are readily converted to acetals with additionalalcohol. If desired, the hemlacetal esters may be formed with onealcohol and these esters converted to mixed acetals with a differentalcohol. Excess alcohol in the reaction is oftentimes desirable, servingas a convenient solvent medium. Other solvents, such as thehydrocarbons, may, however, be used.

The reactions of this invention may be effected at temperatures frombelow room temperature, such as C. to C., up to temperatures of 65 C. to75 C. The preferred temperature range is 25 C. to 50 C. Since in somecases it has been observed that side reactions occur as the temperatureis raised, it is desirable to control temperature, as reactants aremixed, by

conventional methods such as rate of addition of fled. The acetals fromthe larger ether alcohols are obtained primarily as residues.

By the method of this invention, there may be obtained not only knownacetals but also many acetals which have not hitherto been prepared. Theproducts have a wide utility. They are useful, for example, asintermediates for the preparation of many other types of compounds,including many not prepared before. They also serve as solvents andplasticizers.

Specific details of typical preparations of various acetals are providedby the following examples.

' Example 1 There were placed in a reaction vessel equipped withstirrer, thermometer, reflux condenser, and dropping funnel 348 grams ofallyl glycolate, HOCH2COOCH2CH=CH2, one gram of mercury oxide, and onemilliliter of the coordination complex of methyl alcohol and borontrifluoride. To this mixture there was added during the course of aboutone hour 135 grams of vinyl acetate. The temperature of the reactionmixture was controlled at 25 C. to 35 C. by a cooling bath.

' The reaction mixture was then stirred for three and a half hours,whereupon three hundred milligrams of water was'added followed by eightygrams of soda ash in successive small portions. The amount of soda ashcorresponded to that required for neutralization of the reactionmixture.

An oil layer formed and was separated from an aqueous layer. The oillayer was dried over anhydrous potassium carbonate and distilled underreduced pressure at 110 C.-140 C. at 3 mm. The yield of product was 333grams. The distillate was carefully fractionated through a column packedwith an aluminum jack chain. The main fraction was collected at 140 C.at 2 mm. and was identified as allyl glycolate acetal.

Example 2 The reaction vessel was charged with 160 grams of methanol,two grams of mercuric oxide, and two milliliters of the methylalcohol-boron trifluoride complex used above. There was added 260 gramsof vinyl acetate with stirring. The temperature was held at 50 C.- C.The reaction mixture was then stirred for about an hour and then treatedwith about two grams of potassium carbonate to destroy the acidiccatalyst. The liquid was then distilled. A fraction boiling at 55 C. to68 C., amounting to 231 grams, was methyl acetal. An intermediatefraction was then taken, amounting to 21 grams. Then a fraction wastaken at 110 C. to 117 C.,

which was acetic acid. The first fraction was one component to the otheror by external cool- 1 analyzed and found to contain 99% methyl acetal,corresponding in its properties with those described in the literature.

Example 3 lactate acetal.

Example 4 To a mixture of eight gram moles of allyl alcohol, one gram ofmercuric oxide, and two milliliters of CHMDI-LBF: there was slowly addedone gram mole of vinyl acetate. The temperature was held below 50 C. bycooling. After the reaction mixture had been stirred for two hours, itwas treated with water and neutralized with soda ash. The resulting oillayer was separated, dried, and fractionated. The fraction boiling at148 C. to 150 C., amounting to 65% of the estimated yield, was found tobe pure allyl acetal.

Example The procedure of Example 4 was followed with substitution ofisopropanol for the allyl alcohol. The fraction boiling at 125 C to 128C. was found to be pure isopropyl acetal.

Example 5- A mixture of four gram moles of ethyl alcohol, two grams ofmercuric oxide, and two milliliters of CHaOHBFs was placed in a reactionvessel and one gram mole of vinyl acetate slowly added. The reactiontemperature was 40 C. to 52 C. and the stirring time after combinationof reactants about two hours. The reaction mixture was then carefullyneutralized with a dilute alkali solution and the oil layer separated,washed, dried, and distilled. A yield of 92.5% of ethyl acetal wasobtained.

Use of vinyl butyrate in place of the above acetate yields ethyl acetallikewise.

Example 7 Example 8 To a mixture of two gram moles of 2-ethylhexy1alcohol, one gram of mercuric oxide, and one milliliter of CHaOHBFathere was slowly added 0.9 mole of vinyl acetate. The temperature washeld at 45 C. to 50 C. The mixture was then stirred for several hours,treated with water, neu=- tralized, and separated. The oil layer wasdistilled under reduced pressure. The fraction boiling at 150-155 C. at10 mm. was 2-ethylhexyl acetal in a yield of 86%.

Example 9 The procedure of Example 8 was followed, substituting acommercial dodecyl alcohol (from coconut oil by hydrogenation andfractionation). A 94% yield of the corresponding acetal was obtained,distilling at 200 C. at 3 mm. pressure.

Example 10 To a mixture of two gram moles of butoxyethanol, one gram ofmercury oxide, and one milliliter of the coordination complex of borontrifluoride and ethanol, there was gradually added vinyl acetate (1.1moles) while the mixture was stirred and maintained at about 45 C. .to50 C. The reaction mixture was stirred several hours and thenneutralized, and the oil layer was separated and worked up as above. Thefraction distilled at C.-14l C. at 9 mm. pressure was the desiredacetal.

Example 11 A mixture of two gram moles of vinyl acetate, onegram ofmercuric oxide, and two grams of the boron trifluoride-acetic acidcomplex was reacted with two gram moles of ethylene chlorohydrln at 0 C.to 10 C. After this reaction mixture had been stirred for a while, twogram moles of allyl alcohol were added and the reaction mixture leftstirring overnight. Thereupon, it was neutralized, washed, andfractionated. The fraction boiling at 76 C. to 82 C. at 15 mm. wasprimarily the mixed chloroethyl allyl acetal.

Example 12 A mixture of five gram moles of ethylene chlorohydrin, onegram of mercury oxide, and two milliliters of CHa0H. BFa was reactedwith a gram mole of vinyl acetate at 44 C.48 C. After the reactionmixture had been washed, it was separated, dried, and distilled. Thefraction boiling at 105 C. to 106 C. at 13 mm. was beta-chloroethylacetal. The yield was 52%.

Example 13 Four gram moles of vinyl acetate were reacted with four grammoles of ethylene glycol, with two grams of mercury oxide and fourmilliliters of CHaOHBF: serving as the catalysts. The reaction mixturewas neutralized, washed, and separated. The oil layer contained thecyclic acetal, 4-methy1 dioxalane, boiling at 82 C.

Example 14 To a mixture of two gram moles of butoxyethoxyethanol, onegram of mercury oxide, and one milliliter of CHaOI-LBF: there was addedat 45 C.-50 C. 1.1 gram moles of vinyl acetate. The reaction mixture wasstirred for two hours. neutralized, and separated. An 82% yield of thedesired acetal was obtained, boiling at 158 C.- 160 C. at 2 mm.

Example 15 The procedure of Example 14 was followed with substitution of2-ethyl hexoxyethanol as the alcohol. A yield of 73% of hexoxyethylacetal was obtained, distilling at 189 C.-191 C. at 2 mm.

Example 16 To a mixture of four gram moles of methyl alco- 1101, onegram of mercury oxide, and 0.5 cc. of concentrated sulfuric acid, therewas added at 45 C.-55 C. two gram moles of vinyl acetate.

The mixture was stirred for about forty-five minutes ,and then worked upwith neutralization and distillation. A yield of 65% of the desiredmethyl acetal was obtained.

Example 17 To a mixture of two gram moles of vinyl acetate, one gram ofmercury oxide, and one milliliter of CEOHBFa, there was added at about20 C. two gram moles of methyl alcohol. Then, two gram moles of n-butylalcohol were run in and the temperature allowed to rise to 35 C. Thereaction mixture was stirred for about twenty minutes and thenneutralized. The product obtairied was predominantly the mixed methylbuty ace 2.].

Example 18 To a mixture of 138 grams of phenoxyethanol,

one gram of mercury oxide, and one milliliter of methyl alcohol-borontrifiuoride catalyst, there auaoao was added at about 40 C. 43-grarns ofvinyl acetate. The temperature gradually rose to 60 C. and stirring wascontinued, after all of the ester had been added, for about twentyminutes. Thereupon two grams of potassium carbonate were added andstirred into the reaction mixture. The mixture was settled, decanted,and distilled under reduced pressure. Acetic acid was taken off up to 60C. at 11 mm. and an intermediate fraction of 30 grams from 60 C. to 184C. at 2 min. Then the main fraction, amounting to 98 grams ofphenoxyethyl acetal. distilled at 184 C.-l86 C. at 2 mm.

Emample 19 In a two-liter, three-necked, round-bottomed flask there wereplaced 150 grams of dodecyloxyethanol, one gram of mercuric oxide, andfive milliliters of the boron trifluoride complex of methanol. The flaskand contents were warmed to 40 C. and '22 grams of vinyl acetate wereslowly added. During the addition the flask was cooled externally tohold the temperature at 50 C. Then the reaction mixture was stirred foran hour, during which time the temperature was held at 50? C. to 55 C.It was then treated with 200 grams of water and neutralized with 14grams of soda ash. Layerswere allowed to form which were separated. Theupper layer was dried with anhydrous sodium sulfate and distilled.Unreacted ether alcohol was taken off at 126 C. at 2 mm., followed by afraction distilling between 126 C. and 179 C. at 2 mm., leaving aresidue of 29 grams corresponding in composition to dodecyloxyethylacetal. This product has a melting point of +30 F., viscosities of 3.00cs. at 210 F. and of 10.52 cs. at 100 F., and a viscosity index of 160.

Example By the procedure detailed in Example 19 there were mixed 246grams of oleyloxyethoxyethanol, one gram of mercuric oxide, 5milliliters of the boron trifluoride-methanol complex, and 33 grams ofvinyl acetate. After reaction had been carried on for an hour, thereaction mixture was neutralized with grams of sodium carbonate. Thelayers which formed were separated. The

product was dried over potassium carbonate and distilled therefrom.Material distilling up to 190 C. at 1 mm. was taken off, leaving aresidue of 83 grams corresponding in composition to the acetal of theether alcohol used. The viscosities of this product were 7.93 es. and3.33 cs. at 100 F. and 210 F., respectively.

The acetals which are prepared according to the method of this inventionare prepared from a vinyl ester, particularly a vinyl ester of asaturated aliphatic monocarboxylic acid of two to four carbon atoms,under the influence of a mercury catalyst and an acidic catalyst, byreaction with an ether alcohol of the formula wherein R is a hydrocarbongroup, R" is an alkylene group of two to three carbon atoms, and :r isan integer, particularly an integer from one to five. R may be any typeof hydrocarbon group including aliphatic, arylaliphatic, cycloaliphatic,or aryl, or combinations thereof, and preferably contains one toeighteen carbon atoms. The integer n: is not limited to a value of fivebut may be larger since polyalkylene ethers are readily prepared withsix to twelve ether groups, or even more, as is known. The etheralcohols yield a highly interesting and useful class of ether acetals.Many of these remain liquid at very low temperatures and yet have veryhigh boiling points. They are powerful solvents for many types oforganic compounds. These properties support uses for the ether acetalsas solvents, carriers, plasticizers, softeners, and the like.

We claim:

1. A process for preparing ether acetals which comprises reacting at 0C. to 75 C. in the presence of a mercury catalyst and a strongly acidiccatalyst a vinyl ester of a saturated monocarupper layer was dried andsubjected to fractional distillation. Oleyloxyethoxyethyl acetal wasobtained as a residue, after al1 material distilling up to 210 C. at 2mm. had been taken off. This acetal had viscosities of 5.15 cs. and10.00 cs. at 210 F. and 100 F., respectively.

Example 21 Example 22 By the general procedure of the last threeexamples there were reacted 122 grams of2-ethylhexyloxyethoxyethoxyethoxyethoxyethanol and 16.5 grams or vinylacetate in the presence of two grams of mercury oxide and 5 cc. of borontrifluoride-methanol complex. In this case the boxylic acid of two tofour carbon atoms and an ether alcohol of the formula wherein R is ahydrocarbon group, R" is an alkylene group of two to three carbon atoms,and a: is an integer from one to twelve, destroying the acidic catalystin the reaction mixture, and separatingtherefrom an ether acetal.

2. A process for preparing ether acetals which comprises reacting at 0C. to 75 C. in the presence of a strongly acidic catalyst and of amercury catalyst a vinyl ester, RCOOCH=CHa wherein R is an alkyl groupof one to three carbon atoms, and a more than equivalent proportion of anontertiary ether alcohol of the formula wherein R is a hydrocarbongroup of one to eighteen carbon atoms, R" is an alkylene group of two tothree carbon atoms, and a: is an integer from one to five, destroyingthe acidic catalyst in the reaction mixture, and separating therefrom anether acetal.

3. A process for preparing ether acetals which comprises reacting at 0C. to 75- C. in the presence of mercury oxide and a boron trifluoridecatalyst one mole of vinyl acetate and two moles of an ether alcohol ofthe formula wherein R is an alkyl group of one to eighteen carbon atoms,R" is an alkylene group of two to three carbon atoms, and a: is aninteger from one to five, neutralizing the reaction mixture, andseparating therefrom an ether acetal.

9 4. A process for preparing ether acetals which comprises reacting at 0C. to 75 C. in the presence of mercury oxide and a boron triiiuoridecatalyst one mole of vinyl acetate and two moles of an ether alcohol ofthe formula R'(OR"):OH

wherein R is a phenyl hydrocarbon substituent, R" is an alkylene chainof two carbon atoms. and a: is an integer from one to twelve.

5. A process of preparing ether acetais which comprises reacting at 0 C.to 15 C. in the presence of a small amount of mercury oxide and a borontriiiuoride catalyst one mole of vinyl acetate and two moles of aphenoxyethanol, destroyina the acidity of the reaction mixture, andseparating therefrom an acetal.

6. A process of preparing dodecyloxyethyl acetal which comprisesreacting one mole of vinyl acetate with two moles of dodecyloxyethanolin the presence of a. small amount of mercury oxide and a borontrifluoride catalyst, destroying the acidity of the reaction mixture,and separating therefrom dodecyloxyethyl acetal.

WILLARD J. OROXALL. HARRY T. NEHER;

